1. Field of the Invention
The present invention relates to an optical transmission system, and more particularly to a self-healing bit rate transducer in an optical cross-connection device.
2. Description of the Related Art
In general, diverse protocols and bit rates can be employed in an optical transmission system. Some examples of such protocols includes the fiber distributed data interface (FDDI), the enterprise system connectivity (ESCON), the optical fiber channel, Ethernet, the asynchronous transfer mode (ATM), etc., and their bit rates are 124 Mb/s, 155 Mb/s, 200 Mb/s, 622 Mb/s, 1062 Mb/s, 1.25 Gb/s, 2.5 Gb/s, respectively.
A single protocol and bit rate are typically employed for each of above protocols in an optical transmission system, and the bit rate of an optical signal is pre-set in such a system. Hence, an optical receiver installed in a transmitter or a terminal, etc. is typically designed to exclusively meet the pre-set protocol and the bit rate. Typically, systems for transmitting digital data, especially on an optical link, the quality of transmission depends largely on the performance of the transmitter and the receiver.
FIG. 1 is a block diagram illustrating an optical cross-connection device (OXR) employing an electric switch according to the conventional art system. Referring to FIG. 1, the conventional OXR includes a demultiplexer (DEMUX) 106 for demultiplexing inputted optical signals according different channels and for outputting the same; a plurality of photo-electric transducers 102 with a steady bit rate for transducing an optical signal outputted from the DEMUX 106 into the corresponding electric signal; an OXR switch 103 for pass-routing and outputting the electric signal inputted from the plurality of optical transducers 102 at a steady bit rate; a plurality of electro-optic transducers 104 with a steady bit rate for transducing the electric signals outputted from each output port of the OXR 103 into the corresponding optical signals and for outputting the same; and, a multiplexer 107 for multiplexing the optical signals 105 outputted from the plurality of electro-optic transducers 104 at a steady bit rate through a single optical fiber and outputting the same. Here, the OXR switch 103 is controlled by a controller 108.
As the OXR device in the conventional optical transmission system houses the photo-electric transducer (optical receiver) at a steady bit rate and the electro-optic transducer (optical transmitter) at a steady bit rate, the connection is performed under a predetermined type of steady transmission format. This means that the OXR device in the conventional optical transmission system lacks adaptability to the variation in the transmission format and the varying bit rate. Hence, the limitation of a cross connection capability only in a steady data network poses a problem in multiple transmission and network management.
A co-pending U.S. patent application Ser. No. 09/621,009 filed earlier by the same applicant on Jul. 20, 2000, entitled “Method and Device for Optical Receiving Not Relying on a Bit rate, discloses the construction of a transduction for informing the bit rate using only a data DC level value. In the co-pending application, the controller sections inside each of the transmission section and receiving section recognize the variation of the bit rate. However, another central controller that is costly needs to be housed therein. This patent application further discloses some drawbacks in that the information on the bit rate is relied on the data DC level value only, thereby resulting in errors in recognizing the bit rate if there is any variation in the temperature within the system.